1. Field of the Invention
Aspects of the present invention relate to an image forming apparatus and a power transmission unit thereof, and more particularly, to an image forming apparatus and a power transmission unit in which mechanical or rotational power for a developing device can be easily connected by a user when the developing device is mounted to or detached from the inside of the image forming apparatus.
2. Description of the Related Art
In general, an image forming apparatus outputs a predetermined image onto a printing paper or an electronic file. The image forming apparatus is classified into an electrophotographic type, an ink jet type, and a direct thermal type according to a method by which an image is formed. The electrophotographic type image forming apparatus forms an image through a series of processes, such as electrification, exposure, developing, transfer, and fusing. A laser printer and a photocopier are examples of such an electrophotographic type image forming apparatus.
Recently, among laser printers, a color laser printer which forms a color image by using a plurality of toners, including Yellow, Magenta, Cyan, and Black (YMCK), has become more prevalent. A plurality of developing devices used to accommodate each of the YMCK color toners are provided detachably from a laser printer main body so as to facilitate replacement of the toner and repair of a paper jam.
These developing devices comprise a rotational body such as a photosensitive drum, and a driven assembling member (a male coupling) which is coaxially assembled with the rotational body and receives power from a driving motor (not shown) inside the laser printer when the developing devices are mounted, and a driving assembling member (a female coupling) which is engaged with and disengaged from the driven assembling member coaxially when the developing devices are mounted and is driven by the driving motor.
However, a power transmission unit is needed to engage and disengage the driven assembling member from the driving assembling member when the developing devices are mounted or detached. In Japanese First Publication No. H05-61281, a rotational power selectively connecting apparatus is disclosed to assemble and disassemble a plurality of driven assembling members in one developing device with a plurality of driving assembling members corresponding to the plurality of driven assembling members according to an opening and closing operation of a cover.
However, much force is needed to open and close its cover since the cover and the power transmission unit are assembled with a link so as to engage the opening and closing operation of the cover with an assembling or engaging/disengaging operation of the power transmission unit. In particular, as the number of developing devices or driven assembling members increases, which need to be intermitted, more force is needed to engage/disengage power thereto, thereby causing a user's inconvenience.
Also, if the developing devices have to be mounted and detached or a distance among the driven assembling members is long, such a configuration becomes complicated and lowers compatibility, thereby raising a production cost.